Combine the onions, sugar, wine, and side in a heavy bottomed saucepan.
Create a sachet using cheesecloth to hold the peppercorns, clove, bay leaf, vanilla bean and cinnamon stick, and tie securely with kitchen string.
Add the sachet to the pot and continue to cook over medium high heat until the mixture reaches 225 degrees F., or until the mixture thickens.
Add the vinegar to the jam and stir. Ladle the jam into hot, sterilized jars leaving a 1/4 inch headspace.
Wipe the rims with a warm, clean cloth and secure the lids firmly. Process the jars in a boiling water bath that covers the lids by 1-inch for 10 minutes.
Remove the jars from the water bath and allow to cool to room temperature. Store in a cool dark place before using.
Recipe Notes
Adapted Italian Food Forever (www.italianfoodforever.com)